This disclosure relates generally to redundant memory and voltage island configurations, and more specifically to a semiconductor device and semiconductor device design structure that manages redundant memory in a voltage island.
Redundant memory involves placing extra rows and columns into memory such as random access memory (RAM). Because RAMs are susceptible to the slightest defects in the underlying silicon during fabrication, the extra rows and columns can be used to aid in the repair of these defects. The redundancy makes these RAMs usable despite having small defects and thus prevents having to discard a device containing several RAMs if one or more has a minor defect that can be repaired.
Although a voltage island can be used in a couple of different capacities, a typical voltage island is a region of an integrated circuit that can be powered on and off independently of the rest of the components of the integrated circuit. One particular area where a voltage island that operates in this capacity is suitable for use is with cellular phones. Generally, when a cellular phone is not in use, approximately 98% of its integrated circuit components are turned off and the remaining 2% of the components are kept powered up, waiting for a call to come in or for a user to press the phone keypad to initiate a call. Receiving a call or pressing the telephone keypad will initialize the rest of the components within the integrated circuit.
The integrated circuit components that are used in a cellular phone can have more than one voltage island containing more than one RAM with redundancy that functions as a region that is power cycled (i.e., turned on and off) and one or more non-power cycled regions (i.e., always on) that has more than one RAM with redundancy. Determining how best to distribute repair data and update the redundant RAMs with the data is a challenge because manufacturers do not want to use configurations that will waste area by increasing integrated circuit components and thus increase costs or increase power usage by needlessly having additional components remain always on.